This invention relates to a device and method for regulating the start of fuel injection in an internal combustion engine.
Because of the growing demand for minimizing emissions from Otto engines an increasing amount of interest has been shown in sequential computer controlled injection of fuel to the inlet valves. Sequential injection, where the fuel is injected individually for each cylinder to the inlet valve, where the cylinder is already in or at the beginning of the intake stroke, provides more precise dosing of the fuel before each combustion. There are a number of patents on computer controlled sequential injection. In U.S. Pat. No. 4,785,784 and U.S. Pat. No. 4,961,411 two computer controlled injection systems are described in which two injections per cylinder take place for each intake stroke, and in which the second injection provides a correcting quantity if the fuel requirement has been changed since the first injection was initiated. The purpose of this is to ensure a faster response in transient load cases. The two-stage injection in these patents generally takes place as a split injection, and also mainly whilst the inlet valve is open. Other solutions for reducing emissions include atomization of the fuel by evaporation on beating elements inserted in the intake duct immediately upstream from the inlet valve. Patents U.S. patent Application No. 4,967,706(=EP,A,343652) and DE,C,3426469 describe loose inserts which are heated with PTC elements. The disadvantage of these is that after the engine has warmed up the elements are cooled by the air flow, which renders evaporation difficult unless the heating plate is continuously heated electrically, and that the current consumption is very high, particularly in the case of a cold start. Other solutions are described in patents DE,A,4020266 and DE,A,4020267, where nearing elements are drilled into the cylinder head near the walls of the intake ducts, the disadvantage here being that the entire cylinder near constitutes a cooling body during the warming up phase, thereby necessitating a high current consumption for the intended heating of the walls. U.S. patent Application No. 4,378,001 describes a variant with the heating plate recessed in the intake manifold. U.S. patent Application No. 5,056,495 describes a heating plate permanently arranged in the intake manifold, on to which the fuel is injected directly for further distribution to the intake duct. The above-mentioned solutions involve directed injection to a heating plate which requires heating and hence continuous current consumption. U.S. patent Application No. 5,048,500 describes a heating plate which can be swivelled into the air flow and is arranged upstream of the inlet valve, but where the fuel nozzle is directed toward the heating plate arranged in the intake duct upstream from the inlet valve.